1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * All rights reserved. 11 * 12 * This software was developed at the Centre for Advanced Internet 13 * Architectures, Swinburne University of Technology, by Lawrence Stewart, James 14 * Healy and David Hayes, made possible in part by a grant from the Cisco 15 * University Research Program Fund at Community Foundation Silicon Valley. 16 * 17 * Portions of this software were developed at the Centre for Advanced 18 * Internet Architectures, Swinburne University of Technology, Melbourne, 19 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 20 * 21 * Redistribution and use in source and binary forms, with or without 22 * modification, are permitted provided that the following conditions 23 * are met: 24 * 1. Redistributions of source code must retain the above copyright 25 * notice, this list of conditions and the following disclaimer. 26 * 2. Redistributions in binary form must reproduce the above copyright 27 * notice, this list of conditions and the following disclaimer in the 28 * documentation and/or other materials provided with the distribution. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 */ 42 43 /* 44 * This software was first released in 2007 by James Healy and Lawrence Stewart 45 * whilst working on the NewTCP research project at Swinburne University of 46 * Technology's Centre for Advanced Internet Architectures, Melbourne, 47 * Australia, which was made possible in part by a grant from the Cisco 48 * University Research Program Fund at Community Foundation Silicon Valley. 49 * More details are available at: 50 * http://caia.swin.edu.au/urp/newtcp/ 51 */ 52 53 #include <sys/cdefs.h> 54 __FBSDID("$FreeBSD$"); 55 56 #include <sys/param.h> 57 #include <sys/kernel.h> 58 #include <sys/malloc.h> 59 #include <sys/module.h> 60 #include <sys/socket.h> 61 #include <sys/socketvar.h> 62 #include <sys/sysctl.h> 63 #include <sys/systm.h> 64 65 #include <net/vnet.h> 66 67 #include <netinet/tcp.h> 68 #include <netinet/tcp_seq.h> 69 #include <netinet/tcp_var.h> 70 #include <netinet/cc/cc.h> 71 #include <netinet/cc/cc_module.h> 72 73 static void newreno_ack_received(struct cc_var *ccv, uint16_t type); 74 static void newreno_after_idle(struct cc_var *ccv); 75 static void newreno_cong_signal(struct cc_var *ccv, uint32_t type); 76 static void newreno_post_recovery(struct cc_var *ccv); 77 78 struct cc_algo newreno_cc_algo = { 79 .name = "newreno", 80 .ack_received = newreno_ack_received, 81 .after_idle = newreno_after_idle, 82 .cong_signal = newreno_cong_signal, 83 .post_recovery = newreno_post_recovery, 84 }; 85 86 static void 87 newreno_ack_received(struct cc_var *ccv, uint16_t type) 88 { 89 if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) && 90 (ccv->flags & CCF_CWND_LIMITED)) { 91 u_int cw = CCV(ccv, snd_cwnd); 92 u_int incr = CCV(ccv, t_maxseg); 93 94 /* 95 * Regular in-order ACK, open the congestion window. 96 * Method depends on which congestion control state we're 97 * in (slow start or cong avoid) and if ABC (RFC 3465) is 98 * enabled. 99 * 100 * slow start: cwnd <= ssthresh 101 * cong avoid: cwnd > ssthresh 102 * 103 * slow start and ABC (RFC 3465): 104 * Grow cwnd exponentially by the amount of data 105 * ACKed capping the max increment per ACK to 106 * (abc_l_var * maxseg) bytes. 107 * 108 * slow start without ABC (RFC 5681): 109 * Grow cwnd exponentially by maxseg per ACK. 110 * 111 * cong avoid and ABC (RFC 3465): 112 * Grow cwnd linearly by maxseg per RTT for each 113 * cwnd worth of ACKed data. 114 * 115 * cong avoid without ABC (RFC 5681): 116 * Grow cwnd linearly by approximately maxseg per RTT using 117 * maxseg^2 / cwnd per ACK as the increment. 118 * If cwnd > maxseg^2, fix the cwnd increment at 1 byte to 119 * avoid capping cwnd. 120 */ 121 if (cw > CCV(ccv, snd_ssthresh)) { 122 if (V_tcp_do_rfc3465) { 123 if (ccv->flags & CCF_ABC_SENTAWND) 124 ccv->flags &= ~CCF_ABC_SENTAWND; 125 else 126 incr = 0; 127 } else 128 incr = max((incr * incr / cw), 1); 129 } else if (V_tcp_do_rfc3465) { 130 /* 131 * In slow-start with ABC enabled and no RTO in sight? 132 * (Must not use abc_l_var > 1 if slow starting after 133 * an RTO. On RTO, snd_nxt = snd_una, so the 134 * snd_nxt == snd_max check is sufficient to 135 * handle this). 136 * 137 * XXXLAS: Find a way to signal SS after RTO that 138 * doesn't rely on tcpcb vars. 139 */ 140 if (CCV(ccv, snd_nxt) == CCV(ccv, snd_max)) 141 incr = min(ccv->bytes_this_ack, 142 ccv->nsegs * V_tcp_abc_l_var * 143 CCV(ccv, t_maxseg)); 144 else 145 incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg)); 146 } 147 /* ABC is on by default, so incr equals 0 frequently. */ 148 if (incr > 0) 149 CCV(ccv, snd_cwnd) = min(cw + incr, 150 TCP_MAXWIN << CCV(ccv, snd_scale)); 151 } 152 } 153 154 static void 155 newreno_after_idle(struct cc_var *ccv) 156 { 157 int rw; 158 159 /* 160 * If we've been idle for more than one retransmit timeout the old 161 * congestion window is no longer current and we have to reduce it to 162 * the restart window before we can transmit again. 163 * 164 * The restart window is the initial window or the last CWND, whichever 165 * is smaller. 166 * 167 * This is done to prevent us from flooding the path with a full CWND at 168 * wirespeed, overloading router and switch buffers along the way. 169 * 170 * See RFC5681 Section 4.1. "Restarting Idle Connections". 171 */ 172 if (V_tcp_do_rfc3390) 173 rw = min(4 * CCV(ccv, t_maxseg), 174 max(2 * CCV(ccv, t_maxseg), 4380)); 175 else 176 rw = CCV(ccv, t_maxseg) * 2; 177 178 CCV(ccv, snd_cwnd) = min(rw, CCV(ccv, snd_cwnd)); 179 } 180 181 /* 182 * Perform any necessary tasks before we enter congestion recovery. 183 */ 184 static void 185 newreno_cong_signal(struct cc_var *ccv, uint32_t type) 186 { 187 u_int win; 188 189 /* Catch algos which mistakenly leak private signal types. */ 190 KASSERT((type & CC_SIGPRIVMASK) == 0, 191 ("%s: congestion signal type 0x%08x is private\n", __func__, type)); 192 193 win = max(CCV(ccv, snd_cwnd) / 2 / CCV(ccv, t_maxseg), 2) * 194 CCV(ccv, t_maxseg); 195 196 switch (type) { 197 case CC_NDUPACK: 198 if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) { 199 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) 200 CCV(ccv, snd_ssthresh) = win; 201 ENTER_RECOVERY(CCV(ccv, t_flags)); 202 } 203 break; 204 case CC_ECN: 205 if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) { 206 CCV(ccv, snd_ssthresh) = win; 207 CCV(ccv, snd_cwnd) = win; 208 ENTER_CONGRECOVERY(CCV(ccv, t_flags)); 209 } 210 break; 211 } 212 } 213 214 /* 215 * Perform any necessary tasks before we exit congestion recovery. 216 */ 217 static void 218 newreno_post_recovery(struct cc_var *ccv) 219 { 220 int pipe; 221 pipe = 0; 222 223 if (IN_FASTRECOVERY(CCV(ccv, t_flags))) { 224 /* 225 * Fast recovery will conclude after returning from this 226 * function. Window inflation should have left us with 227 * approximately snd_ssthresh outstanding data. But in case we 228 * would be inclined to send a burst, better to do it via the 229 * slow start mechanism. 230 * 231 * XXXLAS: Find a way to do this without needing curack 232 */ 233 if (V_tcp_do_rfc6675_pipe) 234 pipe = tcp_compute_pipe(ccv->ccvc.tcp); 235 else 236 pipe = CCV(ccv, snd_max) - ccv->curack; 237 238 if (pipe < CCV(ccv, snd_ssthresh)) 239 CCV(ccv, snd_cwnd) = pipe + CCV(ccv, t_maxseg); 240 else 241 CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh); 242 } 243 } 244 245 246 DECLARE_CC_MODULE(newreno, &newreno_cc_algo); 247